alpha-phenylacetamido-beta, beta-dialkoxypropionic acid and method for preparing same



: Patented Sept. 26, 1950 UNITED STATES PATENT OFFICE aPHENYLACETAMIDO-B,,B-DIALKOXYPRO- PIONIC ACID AND METHOD FOR PREPAR- INGSAME Stanton A. Harris, Westfield, and Glen E. Arth and Carl H. Hofiman,Rahway, and Karl Folkers, Plainfield, N. 3., assignors to Merck & Co.,Inc., Raliway, N. .L, a corporation of New Jersey No Drawing. Originalapplication December 21,

1945, Serial No. 636,516. Divided and this application September 8,1948, Serial No. 48,334

Claims. (01. 260-471) synthesis of penicillin and compounds possessingpenicillin-like activity.

This application is a division of my co-pending application Serial No.636,516, filed December 21, 1945, now U. S. Patent 2,489,881.

In preparing our new chemical compounds we may start with the methylester of a-fOlIIlYl-aphenacetamido aceticacid, sodium salt, prepared asdescribed in the following examples which are intended to beillustrative, but not restrictive, of

our invention.

' EXAMPLE 1 Methyl penaldate G CHO oemomo ONE-( 111C OOCH;

7 Preparation of a-formyl-a-phenacetamido acetic acid methyl ester,sodium salt A suspension of .25 mole of freshly prepared sodiummethoxide, free from methyl alcohol, was made in ca. 50 ml. dry benzene.To this sus pension was added a solution of 13 grams ofv methyl formate(0.3 mole; 20% excess) and about two-thirds of 52 grams (.25 mole) ofphenacetamidoacetic acid methyl ester in 350 ml. dry benzene withthorough stirring. The remainder of the ester was added as a solid.Reaction began almost immediately; a yellow to orange colorationdeveloped and a precipitated oil began to appear within ten to'fifteenminutes from the'beginning of addition of the ester. Stirring wascontinued for six hours, and the mixture then allowed to standovernight. The crude semi-solid may be used in the following steps afterdecanting the benzene. However, the sodium salt can be solidiperiments,to yield fied and granulated by stirring with a nearly equal volume ofethyl ether, as shown in later ex- -50 grams of crude salt when dried.

The methyl formate used was Eastman Kodak reagent grade, dried overanhydrou potassium carbonate. It had been found to be acid previously. AHershberg stirrer was used. Addition was quite rapid; time consumed wasabout fifteen minutes.

EXAMPLE 2 Dim'trophenylhydrdzone of methyl penaldate G A solution of 2.5N sodium methoxide was prepared by dissolving 5.75 g. sodium in methanoland diluting the product to ml. in a volumetric flask. Eight millilitersof this solution was evapO-. rated to a sludge under reduced pressure.Toluene (15 ml.) was added and the suspension again evaporated to asolid. This solid was then covered with ether (about 50 ml.) and 1.25 g.(0.02 mole) methyl formate added. Phenacetyl glycine methyl ester (4.14g., 0.02 mole) was then added.

The mixture was shaken and a yellow viscous oilseparated. After standingfor an hour or so, the oil became more viscous. Part of this viscousmaterial was dissolved in water and acidified with a hydrochloric acidsolution containing 2,4-dinitrophenylhydrazine.

After two more recrystallizations from methanol, the product melted at180-181 C. (Softens 177.) This product did not depressthe melting pointof a 2,4-dinitrophenylhydrazone obtained from penicillin. Partialanalysis gave the following:

Calcd. for C18H17N507I C, 52.04,; H, 4.13; N, 16.86. Found: C, 51.85; H,3.98; N, 17.19; 16.66;

' EXAMPLE 3 MethyZ-a-phenylacetamido-B,,6-dimetho:rypr0- pionate (methylpenaldate G dimethylacetal) A quantity of 129 grams of methyl-a-formyl-aphenacetainido acetate sodium salt was dissolved A yellow2,4-dinitrophenylhydrazone separated which melted -160 C- .whenrecrystallized from methanol.

in 750 ml. of water. The water solution was extracted three times with50-ml. portions of chloroform, which were discarded. The water layer wasmade thoroughly acid to Congo paper by additions of 50% sulfuric acidandextraction with one portion of chloroform carried on simultaneously.Four more portions were used, the chloroform layers combined and driedover anhydrous sodium sulfate and concentrated. After final removal ofthe solvent under vacuum pump, the residue (light brown oil) of crudeformyl ester weighed 34.4 gms.

This oily ester was treated with 150 ml. of dry methanol in whichapproximately g. of dry hydrogen chloride gas had been dissolved. Aftershaking for a time to put in solution, it was allowed to stand at roomtemperature for one hour. The methanol was then concentrated down toabout one-third original volume, 100 ml.of chloroform added to thecooled residue and this solution shaken with a half liter of water,which was. extracted four more times with a little chloroform. The.combined chloroform extracts were shaken once more with water, then withwater containing enough sodium bicarbonate to remain basic (added asneeded). The chloroform layer was dried over anhydrous sodium sulfateand concentrated. The residue of crude acetal ester was 22.5 grams afterfinal drying under high vacuu to a viscous brown oil.

EXAMPLE 4 a-Phenylacetamido-p,c-dimethozcypropionic acid (penaldic Gacid, dimethylacetal) This material was treated with 88 ml. of normalsodium hydroxide (1 equivalent) and enough methanol added to put the oilinto solution. This solution is allowed to stand at room temperature oneand one-half hours; it is then concentrated down to about one-third itsoriginal volume, diluted. with 250 ml. of water, and the solutionextracted three times with 50-ml. portions of chloroform, which arediscarded. The water layer is acidified slowly by addition of 50%sulfuric acid,

keeping the solution cool, and simultaneously extracting theprecipitated acid with cholorform until further addition of sulfuricacid produces no precipitate in the water layer.

The water layer is extracted four more times with 50-ml. portions ofchloroform, and the chloroform layers combined, dried over anhydroussodium sulfate and concentrated. The residual viscous oil, after finaldrying, weighed 12.5 grams. This crude acid is dissolved in a 1-1mixture of ethyl acetate and petroleum ether with refluxing, and treatedwith 2 to 3 grams of Darco-G-60 activated carbon which removes somecolor. To the filtered liquor is added more petroleum ether untilincipient cloudiness at room temperature. On standing overnight in theicebox, 2.5 grams of acid melting at 109-111 C. (unc.) deposited.

Partial analysis gave the following:

Calcd. for C13H1'1O5N2 C, 58.42; H, 6.42; N, 5.24..

Found: C, 58.00, 58.11; H, 6.45, 6.26; N, 5.15.

EXAMPLE 5 Benzylamide of a-phenylacetamido-c,/3-dimethomypropionic acid(penaldic G dimethylacetalbenzylamide) A mixture of one gram offi,/3-dimethoxy-aphenylacetamidopropionic acid, methyl ester and onegram of benzylamine was heated at 120-130 C. for two hours. A smallsample of the oily product in ether-petroleum ether deposited crys' talswhen scratched. On cooling, scatching am seeding the reaction mixture inether, a crystalline solid separated. When recrystallized from methanol,needles separated melting at 164-165 C.

Partial analysis gave the following:

Found: C, 67.53, 67.67; H, 6.48, 6.76; N, 8.07.

EXAMPLE 6 ,B-Methoxy-a-phenylacetamidoacrylic acid A solution of '1fifi-dimethoxy-a-phenylacetamido propionic acid in 5 ml. aceticanhydride containing three drops of piperidine and 0.2 g. sodium acetatewas heated on a steam bath for one-half hour. The cooled reactionmixture was extracted with petroleum ether. The petroleum ether wasconcentrated to an oil. A small portion of this oil was placed in asublimer and heated under reduced pressure. The drop which collected onthe condenser was scraped into a test tube and treated with milliliterof ether and scratched. Crystals separated. When recrystallized fromethyl acetate, a product was obtained melting at 199-200 C. (uncorr.).Recrystallization did not raise the. melting point. (193.5-1945" corr.)

Partial analysis gave the following:

Calcd. for C12H13NO4; C, 61.28; H, 5.57; N, 5.96. Found: C, 61.31; H,5.55; N, 6.24, 6.30.

EXAMPLE 7 Z-benzyl-sl-metho:cymethyZene-5(4) -0arazolone Sixty-six gramsof li e-dimethoxyphenacetamidopropionic acid, M. P. 113-115 C., wasplaced in a round bottom fiask together with ml. of acetic anhydride andthe mixture heated on the steam bath. The solid dissolved slowly until aclear light-colored solution was obtained. This solution was heated forten minutes longer in order to complete the reaction. This additionalheating has been found to be necessary, as working up without it givesonly unreacted starting material. The reaction mixture was concentratedunder reduced pressure in order to remove acetic acid and excess aceticanhydride and then washed with about 200 ml. petroleum ether, whichcaused the residue to solidify. The resulting solid was recrystallizedfrom a small amount of ethyl acetate using just enough-to bring it intosolution and filter hot. The crystalline product is filtered ofi, washedwith cold ethyl acetate, and driedimmediately by pressing on a poroustile. This final drying prevents the darkening and gumming of thesubstance due to the pressure of solvent and EXAMPLE 82-benzyl-4-hydroxymethylene-5 (4) oxazolone The solution made from 5.8gms. of 2-benzyl- 4-methoxy-methylene-5(4) -oxazolone, 174 ml. of.

water, and 11.6 ml. of 2.5 N sodium hydroxide was shaken ice cold for25-30 minutes. There was a snail amount of solid material present whichwhen isolated proved to be unreacted starting precipitate collected,washed with cold water and dried in a vacuum desiccator over phosphoricanhydride. Yield, 4.2 gms., 85% based on material used; M. P. 1l8-ll8.5C. (dec.).

Although this material precipitated from aqueous solution, it is ourexperience that it can be recrystallized from water only withconsiderable loss. Material with this melting point, however, hadsatisfactory analyses for carbon, hydrogen and nitrogen. The meltingpoint of the pure compound is actually higher than the above givenfigure, values as high as 124-125 C. having been obtained from certainpurified samples.

Partial analysis gave the following:

Calcd. for C11H9O3N2 C, 65.02; H, 4.47; N, 6.89. Found: C, 64.74; H,4.34; N, 6.99.

EXAMPLE 9 2-benzyl-4 benzyZaminomethyZene-5 (4) oxazolone A solution of50 mg. of 2-benzyl-4-methoxymethyleneoxazolone-4 in ether was treatedwith one equivalent of benzylamine in ether (total volume of ether, 3 to4 ml.). A small insoluble precipitate was separated by centrifugation,and the ether solution allowed to stand at room temperature for eighteenhours. After five hours, crystals began to appear. The crystals werewashed with ether and recrystallized in square thin plates from ether;M. P. 114-116 C.

Partial analysis gave the following:

Calcd. for C1sH16N2O22 C, 73.96; H, 5.52; N, 9.59. Found: C, 74.60,73.89; 74.18; H, 5.77, 5.52, 5.40; N, 9.98.

EXAMPLE 1o Penaldic amide-2,4-dinitrophenylhydrazone A suspension of 150mg. of 2-benzyl-4-methoxymethylene-5(4) -oxazolone in ml. concentratedaqueous ammonia was shaken mechanically overnight at room temperature.Near1y all of the oxazolone had dissolved and the deep yellow colorwhich first appeared had nearly all been discharged. The excess ammoniaand water were removed under reduced pressure and dilute hydrochloricacid added until the solution had a pH of 3. This treatment failed toproduce a crystalline product so the reaction mixture was treated withan excess of 2,4-dinitrophenylhydrazine and enough ethanol to givecomplete solution on warming, On scratching and cooling, a yellowflocculent precipitate settled out which melted at 218219 C. after tworecrystallizations from ethanol. This compound did not depress themelting point of a 2,4-dinitrophenylhydrazone obtained from penicillinafter its inactivation with ammonia.

Partial analysis gave the following:

Calcd. for CI'IHlGNGOBI C, 51.00; H, 4.03; N, 20.99. Found: C, 51.31; H,4.28; N, 21.36.

v 6 The chemical reactions occurnngmay be represented as follows: 7

- NaOGH; ofinsomoonnomoooMe MeOOCH OHONa o. 11, oHooNHtt-oooMe H2SO4GHOH H01 OBHBGHZQ O NHCCOOMe CHaOH v t "omoomn olng'omooNntn-oooivleNaOH thenacid OH(OCH3)2 o@H.oH2coNHdHoooH A010 O2-benzyl-4-hydroxymethylene-5 (4)- N=CO B20511; oxazolone Variouschanges and modifications may be made in our invention, as describedherein, without departing from the scope thereof.

We claim:

1. a-Phenylacetamido -B,fldimethoxypropionic acid.

2. Methyl-a-phenylacetamido -p,pdimethoxypropionate.

3. The process that comprises reacting the methyl ester ofa-formyl-phenaceturic acid with anhydrous hydrogen chloride in methanolto form the methyl ester of a-phenylacetamido-B,B-dimethoxypropionicacid,

4. The process that comprises reacting the methyl ester ofa-phenylacetamido-B,B-dimethoxypropionic acid with aqueous alkali andacidifying the reaction mixture to forma-phenylacetamido-fifi-dimethoxypropionic acid.

5. The process that comprises reacting the methyl ester ofa-formylphenaceturic acid with anhydrous hydrogen chloride in methylalcohol, reacting the resulting ester ofa-phenylacetamido-p'fi-dimethoxypropionic acid with aqueous 8 alkali andacidifying the reaction mixture to form OTHER REFERENCESa-pheny1acetamido-fl,5-dimethoxypropionic acid.

STANTON A HARRIS. 4 alxllgzglgan Report, CMR-B I, Feb. 16, 1944, PagesGLEN E. ARTH. CARL H. HOFFMAN 5 patgIgJsohn Report, CMR-U IV, Mar. 15,1944, KARL FOLKERS- Upjohn Report, CMR-U-X, July 10, 1944, REFERENCESCITED page The following references are of record in the sqmbb ReportCMRPSJXMM- 1944,13age file of this paiientz UNITED STATES PATENTS NumberName Date 2,394,967 Kushner Feb; 12, 1946

2. METHYL-A-PHENYLACETAMIDO-B,B-DIMETHOXYPROPIONATE.
 3. THE PROCESS THAT COMPRISES REACTING THE METHYL ESTER OF A-FORMYL-PHENACETURIC ACID WITH ANHYDROUS HYDROGEN CHLORIDE IN METHANOL TO FORM THE METHYL ESTER OF A-PHENYLACETAMIDO-B,B-DIMETHOXYPROPIONIC ACID. 